The Fixed-Wing Is In: America's Cup Sailors Plan to Use Rigid Carbon-Fiber Airfoil on U.S. Entry

The U.S. team for the America's Cup is replacing its boat's mast and cloth mainsail with a hard, fixed wing that is 80 percent larger than a Boeing 747 wing, not to mention difficult and dangerous to maneuver

SAN DIEGO—After more than a year of practicing for the America's Cup, the U.S. team is replacing its boat's lofty 60-meter mast and 620-square-meter cloth mainsail with a hard, fixed wing that is 80 percent larger than a Boeing 747 wing and will tower 58 meters above their giant trimaran's deck. The team, known as the BMW ORACLE Racing Team, will start to practice with and evaluate the high-strength yet lightweight carbon-fiber wing on its 27-meter carbon-composite trimaran later this week.

The Americans have been testing new frontiers with the loads that their massive multihull endures while sailing. Crash helmets, personal floatation devices and other body armor have been de rigueur during BMW ORACLE Racing's practices—even while using a mast and a mainsail, which preceded the wing. During a practice session on November 3, the boat's huge mast snapped and toppled into the Pacific. Thankfully, no one was injured. Although the team's research and development unit has been conducting a forensic evaluation of the mast mishap, another unit has been finishing the assembly of the wing under the cover of a huge tent at the team's base in San Diego, in an attempt to keep the technology a secret from competitors.

The America’s Cup is the oldest actively contested trophy in sport and dates back to a race held in 1851 in England in which the yacht America beat 15 boats representing the Royal Yacht Squadron. Members of the winning America syndicate donated the Cup via a Deed of Gift to the New York Yacht Club on July 8, 1857, specifying that it be held in trust as a perpetual challenge trophy to promote friendly competition among nations. According to an Allianz Economic Report conducted in co-operation with Tom Cannon, dean of Buckingham University Business School, the America's Cup ranks just behind the Olympics and the FIFA World Cup in terms of worldwide direct and indirect economic benefits that accrue to the winner and the event's host city. It is the largest inter-club sporting event in the world in terms of economic scale and impact.

The only other time that a multihull and a wing have been used in the America's Cup was in 1988. Back then, the U.S. team defied tradition when they unveiled an 18-meter catamaran equipped with a wing to compete against New Zealand's 27-meter monohull. Burt Rutan, whose company Scaled Composites went on to win the Ansari X PRIZE for SpaceShipOne, and who worked with John Ronz, David Hubbard and Duncan MacLane on the 1988 wing, reflected on that achievement: "The wing-sail designs were more challenging (than aircraft wing applications) because they needed high lift in both directions and because we had a requirement to vary the wing twist to account for different wind gradients above the sea. An aircraft wing lifts in only one direction and does not have any twist control. On the wing-sail we twisted the third element and thus had to make it torsionally flexible."

The scale of the 21st-century sailboat and wing is astronomical compared with the 1988 vintage. The 1988 wing height was slightly over 30 meters, and its area was approximately 165 square meters. The new wing's main element is a monolithic box with an aerodynamic nose along its leading edge. Hinges at different points along the main element's trailing edge can be adjusted to change the gap between the forward and the aft elements to adjust airflow depending on the wind velocity. The sections of the trailing element can be moved independently to induce camber (the asymmetry between the top and bottom curves of an airfoil), making it possible to flatten and even induce negative camber in the top section as well as camber in the opposite direction in the lower sections.

According to BMW ORACLE Racing, "the primary advantage of the wing over a soft sail is that it is easier to control and does not distort. This makes it easier for the trimmers on board to maintain an optimum aerofoil shape in a wide range of conditions." Unlike conventional monohull and multihull sailboats, the BMW ORACLE team's trimaran sails upwind and downwind at apparent wind angles less than 30 degrees (Monohulls typically sail at between 30 and 40 degrees upwind.) On board the racing machine it always feels as if the wind is in the sailors' faces. The wing technology will improve the trimaran's apparent wind angle, and may enable the multihull to exceed two to 2.5 times wind speed. The upcoming America's Cup challenge will be the first time ever that an onboard engine will be used to assist trimmers in controlling the massive foils by powering hydraulic controls for the wing and the forward sails.

Mark Ott, co-founder and executive vice president of Seattle-based Harbor Wing Technologies, the first company to employ a wing that rotates 360 degrees and uses a multihull as a platform, commented, "BMW ORACLE'S boat represents the pinnacle of race boat design; however, the nature of this design limits the wing sail's range of motion due to the shroud and forestay wires used to support it. This design limitation causes these wing sails to be impractical for use by the average sailor. By not allowing the wing full 360-degree rotational capability in everyday sailing conditions, it is bound to it be held on a shroud wire by the wind and damaged, or worse, possibly causing the boat to capsize."

All eyes will be watching to see how BMW will store the boat and the wing, because the latter is not nearly as easy to take down and stow as a cloth mainsail.

The America's Cup showdown is set to take place in February 2010 in Valencia, Spain.

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